Shapes, Softness and Non-Yrast Collectivity in 186W

TL;DR

This study investigates non-yrast excited states in neutron-rich 186W using inelastic scattering, revealing insights into nuclear shapes, softness, and collectivity through detailed gamma-ray spectroscopy and observed staggering patterns.

Contribution

It extends the known rotational bands in 186W and analyzes their energy staggering patterns, providing new insights into nuclear softness and vibrational behavior at high spins.

Findings

Extended rotational bands up to high spins.

Observed gamma softness and vibrational characteristics.

Detected phase differences in odd-even staggering linked to Coriolis effects.

Abstract

Non-yrast, excited states in neutron-rich $^{186}$W were populated via inelastic-scattering reactions using beams of $^{136}$Xe nuclei accelerated to 725 and 800 MeV. Levels populated in the reactions were investigated via particle-$ \gamma $ coincidence techniques using the Gammasphere array of High-Purity Germanium detectors and the compact heavy-ion counter, CHICO2. The $ K^{\pi} = 2 ^{+} $ ($\gamma$), $ K^{\pi} = 0^{+}$ and $ K^{\pi} = 2^{-} $ (octupole) rotational side bands were extended to spins $ 14\hbar $, $ 12\hbar $, and $ 13\hbar $, respectively. A staggering pattern observed in the energies of levels in the $ K^{\pi} = 2^{+} $ band was found to be consistent with a potential that gets softer to vibration in the $ \gamma $ degree of freedom with increasing spin. The odd-even staggering of states in the $ K^{\pi} = 2^{-}$ band was found to exhibit a phase opposite to that seen in the $ \gamma $ band; an effect most probably associated with Coriolis coupling to other, unobserved octupole vibrational bands in $^{186}$W.